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<title>LangGraph 101: Conditional Routing</title>
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<h1 class="title">LangGraph 101: Conditional Routing</h1>
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<section id="imports-and-state-definition" class="level2">
<h2 class="anchored" data-anchor-id="imports-and-state-definition">Imports and State Definition</h2>
<div id="cell-3" class="cell">
<div class="sourceCode cell-code" id="cb1"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="im">from</span> typing <span class="im">import</span> TypedDict</span>
<span id="cb1-2"><a href="#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="im">from</span> langgraph.graph <span class="im">import</span> StateGraph, START, END</span>
<span id="cb1-3"><a href="#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="im">from</span> IPython.display <span class="im">import</span> Image, display</span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
</div>
</section>
<section id="state-definition" class="level2">
<h2 class="anchored" data-anchor-id="state-definition">State Definition</h2>
<div id="e7fee5a9-ad6f-4c0d-895f-e657543a3e27" class="cell">
<div class="sourceCode cell-code" id="cb2"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="kw">class</span> NumberState(TypedDict):</span>
<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>    number: <span class="bu">int</span></span>
<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a>    result: <span class="bu">int</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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</section>
<section id="node-functions-and-router" class="level2">
<h2 class="anchored" data-anchor-id="node-functions-and-router">Node Functions and Router</h2>
<p>We’ve set up three processing nodes to handle different types of numbers:</p>
<ul>
<li><strong>Positive numbers</strong>: We square the number.</li>
<li><strong>Negative numbers</strong>: We take the absolute value.</li>
<li><strong>Zero</strong>: We leave it as zero.</li>
</ul>
<p>Additionally, we’ve built a router function that decides which path to follow based on the sign of the input number.</p>
</section>
<section id="building-the-conditional-routing-graph" class="level2">
<h2 class="anchored" data-anchor-id="building-the-conditional-routing-graph">Building the Conditional Routing Graph</h2>
<ol type="1">
<li>Start → Router node</li>
<li>Router evaluates the number’s sign</li>
<li>Routes to the appropriate processing node</li>
<li>All branches lead to END</li>
</ol>
</section>
<section id="visualizing-the-graph" class="level2">
<h2 class="anchored" data-anchor-id="visualizing-the-graph">Visualizing the Graph</h2>
</section>
<section id="testing-the-conditional-routing-graph" class="level2">
<h2 class="anchored" data-anchor-id="testing-the-conditional-routing-graph">Testing the Conditional Routing Graph</h2>
</section>
<section id="example-2-text-message-processing-router" class="level1">
<h1>Example 2: Text Message Processing Router</h1>
<p>Let’s create another conditional routing example using text messages. This will demonstrate how to route based on text length and apply different processing strategies.</p>
<section id="text-state-definition" class="level2">
<h2 class="anchored" data-anchor-id="text-state-definition">Text State Definition</h2>
<div id="d461b6b3-fa2e-4e53-b563-75bc8055d3dd" class="cell">
<div class="sourceCode cell-code" id="cb3"><pre class="sourceCode python code-with-copy"><code class="sourceCode python"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="kw">class</span> MessageState(TypedDict):</span>
<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>    message: <span class="bu">str</span></span>
<span id="cb3-3"><a href="#cb3-3" aria-hidden="true" tabindex="-1"></a>    processed_message: <span class="bu">str</span></span>
<span id="cb3-4"><a href="#cb3-4" aria-hidden="true" tabindex="-1"></a>    word_count: <span class="bu">int</span></span></code><button title="Copy to Clipboard" class="code-copy-button"><i class="bi"></i></button></pre></div>
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</section>
<section id="text-processing-nodes-and-router" class="level2">
<h2 class="anchored" data-anchor-id="text-processing-nodes-and-router">Text Processing Nodes and Router</h2>
<p>We’ll route messages based on their length and apply different processing:</p>
<ul>
<li><strong>Short messages</strong> (≤ 10 chars): Convert to uppercase and add exclamation</li>
<li><strong>Medium messages</strong> (11-50 chars): Add a friendly greeting prefix</li>
<li><strong>Long messages</strong> (&gt; 50 chars): Summarize by counting words and truncating</li>
</ul>
</section>
<section id="building-the-text-processing-graph" class="level2">
<h2 class="anchored" data-anchor-id="building-the-text-processing-graph">Building the Text Processing Graph</h2>
</section>
<section id="visualizing-the-text-processing-graph" class="level2">
<h2 class="anchored" data-anchor-id="visualizing-the-text-processing-graph">Visualizing the Text Processing Graph</h2>
</section>
<section id="testing-the-text-processing-router" class="level2">
<h2 class="anchored" data-anchor-id="testing-the-text-processing-router">Testing the Text Processing Router</h2>
</section>
</section>

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